Author Topic: Chandrayaan-2 GSLV MkIII NET January 30 2019  (Read 165148 times)

Offline sanman

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #320 on: 08/12/2018 03:10 AM »
Change to the mission - the lander will do some low orbital passes over the lunar surface before going for landing:


https://timesofindia.indiatimes.com/india/isro-wants-chandrayaan-2-lander-to-orbit-moon-first/articleshow/65370820.cms

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The decision on how many orbits the Lander will make has not yet been taken, but it will be a 100x30 (100km on one side and 30 on the other) elliptical orbit, which means that the entire configuration of the mission has now changed, in effect, causing the delay.

“Earlier, the plan was to gradually go down from 100km and reach 18km from the Moon’s surface. From there, the orientation would change, making the Lander go slightly horizontal for about 8.5km and then we were to change the orientation and velocity further to make the soft landing,” a senior member of the Chandrayaan-2 team said.

Now, as per the revised plans, the Lander has to go around the surface of the moon before entering the descent phase. Scientists working on the project say that this change in plan could have been avoided as the earlier configuration that was cleared would have achieved the main mission goals.

“This additional activity required by the Lander means a host of new hardware added. This is one method of achieving the landing, while the earlier one was another. Our job is to follow what the chairman and other seniors decide and develop things that can successfully complete the mission,” another scientist said.

This has also increased Chandrayaan-2 weight from 3,250kg to 3,850kg, which has prompted some changes, including moving to GSLV MK-III instead of the GSLV MK-II, which would have required an uprate to accommodate the additional weight.

New configuration & soft landing issue

As per the new configuration cleared after the fourth Comprehensive Technical Review (CTR) meeting held on June 19, among other things, the Lander would require a fifth liquid engine to manage the additional load of having to orbit, along with other hardware including a transponder which it earlier didn’t need.

“All these last-minute changes means that we have to test all the new hardware and then begin the fabrication process, which will delay the project. Also, the software algorithms need to change as the mission profile itself has been altered, and even this would need tests,” the scientist said.

“The fifth Centrally mounted 800N Steady State Liquid Engine with additional hardware has been included to mitigate upward draft of dust to craft while landing,” the Isro has found.

Also, the Lander will have a new Lander Leg configuration with increased base diameter (from 3.6m to 4.34m) which is to improve the stability margins.
Why the orbiting

According to the committee, the Lander is now required to orbit so that it can make “assessment of various system performances before the actual critical Powered,” and to do this, the descent phase requires the inclusion of four reaction wheel and its drive electronics as well as two micro Star Sensors (main & redundant) which will enable it to measure the moving velocity and help land.

It will also have transponders for ranging and doppler functions with the antenna configuration and a host of additional supporting systems—power, structure, thermal, etc, will also be added.

Besides, there will be two additional propellant tanks (390L capacity), additional pressurant tank (35.5L capacity) among other changes.


I don't mean to be a backbiter, but I worry that such major changes so near to the targeted launch date may cause rushed re-design and testing, thus increasing the chances of mission failure.

So is all of this being motivated by a desire to do some kind of systems validation ahead of the actual landing?

How do the current and former procedures for Chandrayaan-2 compare to other past attempts at landing on the Moon?
« Last Edit: 08/12/2018 03:34 AM by sanman »

Offline sanman

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #321 on: 08/12/2018 04:02 AM »
So this is the previous landing procedure for Chandrayaan-2, as posted by user Ohsin



In it, there's mention of terrain pattern-matching as part of the landing procedure. Could it be that they don't feel confident of their existing terrain maps, and want to take some fresh shots ("in operando") to match against before landing?

And so this resulting new sharper descent trajectory is why they need the extra hardware, including the extra 5th engine, in order to get the landing down pat?

(Google tells me that LIRAP stands for Laser Inertial Reference and Accelerometer Package)
« Last Edit: 08/12/2018 05:43 AM by sanman »

Offline maint1234

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #322 on: 08/12/2018 05:34 AM »
I believe the spate of issues with the launches last year , including the multiple IRNSS satellite problems has resulted in these decisions to delay. Totally support this decision as the moon is going nowhere but a suboptimal mission will impact morale and make headlines for all the wrong reasons. I would support a further delay if they can somehow extend the rover life from the present 1 moon day, 14 earth days ?

Offline sanman

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #323 on: 08/12/2018 06:07 AM »
If there are going to be these low-altitude passes at 30km height over the lunar surface for terrain mapping, then will the effect of reflected solar heating become a more intense issue to deal with, as compared to what Chandrayaan-1 experienced at its relatively higher 100km altitude above the Moon?

Offline Phil Stooke

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #324 on: 08/12/2018 06:58 PM »
"will the effect of reflected solar heating become a more intense issue to deal with"

No, because the low point will be at 70 degrees south where the surface is cooler, but also the designers will have taken that problem into account. 

" there's mention of terrain pattern-matching as part of the landing procedure. Could it be that they don't feel confident of their existing terrain maps, and want to take some fresh shots ... to match against before landing?"

No - this to help locate the lander.  Its images are compared with previous maps to identify its location, so it can be steered down to a precise landing.  This technology has been described before, e.g. by Astrobotic in the US for the Moon and for future Mars landings as well.  It will help ensure a safe landing by guiding the lander to the pre-selected safe location.

In other news...

https://www.hindustantimes.com/india-news/india-s-second-lunar-mission-to-land-on-moon-with-lander-rover-isro/story-vqoGvAyk6hHuUL4SDa17GJ.html

Launch on or after 3 January 2019, and the lander named Vikram after V. Sarabhai. 

Offline sanman

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #325 on: 08/12/2018 08:12 PM »
Hi, thanks for the responses  :)


No - this to help locate the lander.  Its images are compared with previous maps to identify its location, so it can be steered down to a precise landing.  This technology has been described before, e.g. by Astrobotic in the US for the Moon and for future Mars landings as well.  It will help ensure a safe landing by guiding the lander to the pre-selected safe location.

Yes, I'm aware of what the terrain pattern-matching is meant for - but obviously it has to be done against pre-stored maps of the lunar terrain (presumably based on Chandrayaan-1 data?)

So what I meant was - could it be that ISRO's review team doesn't have enough confidence in the pattern-matching system, or else in the quality of the maps being matched against, so that they wanted to make some low-altitude passes first, to ensure that it all works correctly?

Offline Phil Stooke

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #326 on: 08/12/2018 08:35 PM »
Probably the LRO images would be used for the terrain map, as they would have 2 or 3 times better resolution.  My guess is that the low passes are intended to improve knowledge of the trajectory.  Drop to the final pre-descent orbit and make a couple more orbits while the trajectory is checked, then commit to the final descent.  Otherwise you are going from the higher orbit to the surface in one go.   

Offline sanman

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #327 on: 08/12/2018 08:47 PM »
Probably the LRO images would be used for the terrain map, as they would have 2 or 3 times better resolution.  My guess is that the low passes are intended to improve knowledge of the trajectory.  Drop to the final pre-descent orbit and make a couple more orbits while the trajectory is checked, then commit to the final descent.  Otherwise you are going from the higher orbit to the surface in one go.   

I agree that LRO images would be unsurpassed in quality - but would ISRO even have access to that data for its mission purposes?

Also, given that the new descent trajectory requires the addition of a 5th engine, doesn't that make it sound more strenuous as compared to the original plan? (ie. higher loads, since you have less altitude in which to decelerate from orbital velocity)
« Last Edit: 08/12/2018 08:55 PM by sanman »

Offline Phil Stooke

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #328 on: 08/12/2018 09:30 PM »
LRO images are freely available to anyone in the world via the LRO camera team website and NASA's Planetary Data System.  Chandrayaan 1 images are in principle, but they are much more difficult to access and some - the full set of Moon Impact Probe images - have never been released. 

Offline worldtimedate

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #329 on: 08/12/2018 09:34 PM »
ISRO hopes to launch Chandrayaan-2 between January 3 and Mid-March of 2019.

Source : Isro aims to launch 22 missions in 2019; 50 in 3 years

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Among the key missions to look for in 2019 will be the Chandrayaan-2, Aditya-L1 (India's solar mission) and two demonstration flights of the SSLV (small satellite launch vehicle).

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Isro hopes to start the new year (2019) with the launch of Chandrayaan-2, which has already been delayed owing to multiple changes that were needed. Sivan said that they are looking at a launch window between January 3 and mid-March. "We hope to meet the January 3 date," he said, while confirming TOI's August 12 report that the entire configuration of the mission has changed.

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Offline sanman

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #330 on: 08/16/2018 06:25 AM »
from Nature:

https://www.nature.com/articles/d41586-018-05973-6

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The launch of India’s second spacecraft to the Moon has been delayed for the second time this year. Chandrayaan-2 had been expected to lift off in October, after it was pushed back from its original launch date in April.

Kailasavadivoo Sivan, chair of the Indian Space Research Organisation (ISRO) in Bangalore, told reporters on 12 August that the agency is aiming to launch the craft on 3 January next year — although the mission has a launch window of any time between January and March. Chandrayaan-2 will carry an orbiter that will travel around the Moon; a lander that will attempt India’s first controlled, or soft, landing; and a rover.

Sivan said that there were several reasons for the latest delay, including design changes to ensure a smooth touchdown for the lander. He said these changes have increased the weight of the spacecraft and therefore the amount of fuel needed to complete the mission, which has further added to delays.

Offline sanman

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #331 on: 08/21/2018 11:27 AM »
NASA's Moon Minerology Mapper hits it big, confirming water ice on the Moon:

https://www.nasa.gov/feature/ames/ice-confirmed-at-the-moon-s-poles

The pics seem to show way more ice detected at the South Pole compared to the North Pole - I wonder why. Shouldn't we expect similar apportionment for both poles? What could be the reason for this?
I wonder how this could affect the Chandrayaan-2 mission?

Could Chandrayaan-2 have an opportunity to somehow follow up on the lunar ice data provided by M3?

I wish they'd just put the LIBS instrument thing on a small arm or mast, to give it a better view. How's it supposed to detect much when it's on the rover's underbelly? Curiosity's chemcam wasn't kept so blinkered.

Now that they've shifted to GSLV-Mk3 with its higher payload allowance, and now that they're even upgrading the lander, it would be nice if the rover could be made a little more functional. But I guess that would add to yet another goalpost being shifted at the last minute and delay things further.
« Last Edit: 08/21/2018 11:34 AM by sanman »

Offline sghill

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #332 on: 08/21/2018 11:40 AM »
NASA's Moon Minerology Mapper hits it big, confirming water ice on the Moon:

https://www.nasa.gov/feature/ames/ice-confirmed-at-the-moon-s-poles

The pics seem to show way more ice detected at the South Pole compared to the North Pole - I wonder why. Shouldn't we expect similar apportionment for both poles? What could be the reason for this?
I wonder how this could affect the Chandrayaan-2 mission?

On Mars, the differences are explained by progression of the rotation axis over time, what used to be one of the poles is now facing closer to the sun.

Perhaps the Moon has similarly progressed some even with its rotation stabilized more by the Earth. The northern pole could have regularly pointed more at the sun in the past with the southern pole pointing away from the sun.
Bring the thunder!

Offline Phil Stooke

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #333 on: 08/21/2018 05:03 PM »
Nothing to do with rotation, the answer is topography.  The south pole has more craters with permanent shadow in them than the north pole.  In the north, many craters are largely filled with ejecta from the Imbrium basin impact, so they are not very deep (e.g. Peary) and don't have much shadow area.  In the south, the gigantic South Pole-Aitken basin  (extending from Aitken crater at c. 20 degrees south to the South Pole itself) causes lower topography to begin with (plus mountain blocks which cast shadow), and there are other craters in the area to dig even deeper - Shoemaker, Haworth, Faustini, Amundsen, Cabeus to name only the biggest ones.  The result is much more permanent shadow in the south, and more opportunities for the ice to collect.

Chandrayaan 2 is landing at about 70 degrees south, nowhere near these ice deposits.  They will have to wait for future missions.
« Last Edit: 08/21/2018 05:04 PM by Phil Stooke »

Offline chota

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #334 on: 08/28/2018 11:22 AM »
Chandrayaan-2 Flight profile



Credit: https://twitter.com/sidhant

Offline sanman

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #335 on: 08/28/2018 08:07 PM »
Nothing to do with rotation, the answer is topography.  The south pole has more craters with permanent shadow in them than the north pole.  In the north, many craters are largely filled with ejecta from the Imbrium basin impact, so they are not very deep (e.g. Peary) and don't have much shadow area.  In the south, the gigantic South Pole-Aitken basin  (extending from Aitken crater at c. 20 degrees south to the South Pole itself) causes lower topography to begin with (plus mountain blocks which cast shadow), and there are other craters in the area to dig even deeper - Shoemaker, Haworth, Faustini, Amundsen, Cabeus to name only the biggest ones.  The result is much more permanent shadow in the south, and more opportunities for the ice to collect.

Chandrayaan 2 is landing at about 70 degrees south, nowhere near these ice deposits.  They will have to wait for future missions.

So is the difference in topography at the southern pole compared to the northern pole entirely because of where that large asteroid impacted (that created Imbrium basin)?

Offline worldtimedate

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #336 on: 08/28/2018 08:27 PM »
Window to launch Chandrayaan-2 will be between Jan 3 and Feb 16: Isro chief

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Indian Space Research Organisation (Isro) will launch its second moon mission 'Chandrayaan-2' carrying an orbiter, a lander and a rover between January 3 and February 16 next year. During a media interaction, Isro chairman K Sivan said, "We have a window of opportunity to launch the mission between January 3 and February 16. We will try our best to launch the mission during this window."

He said "Chandrayaan-2 will be the first mission in the world going near the "south pole", where recently Nasa's payload M3 on Chandrayaan-1 discovered ice in the shadow of craters.

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The Chandrayaan-2 spacecraft will carry an orbiter, a lander and a rover. The lander carrying a rover will make a soft-landing on the south pole of the moon and the "rover will spend a full lunar day (14 Earth days) there to make the most of the day time performing experiments. "

The rover will walk 100 metres and analyse the content of the lunar surface. It will also perform several experiments using payloads it will be carrying. The orbiter and rover will send back photographs of the moon within 15 minutes. The Isro chairman revealed that the "mass of Chandrayaan-2 has been increased to 3.8 tonnes and will be launched by GSLV-MK-III", instead of GSLV Mk II as planned earlier.

Offline sanman

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #337 on: 08/28/2018 08:49 PM »
So I made a joke before - but is there going to be an actual co-passenger on the Chandrayaan-2 lunar mission, in the form of a small rover from the Netherlands?

http://www.vhf.cz/soubory/dokumenty/poster-pi9cam-activities.pdf

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Dutch lunar rover mission
By the end of 2018 or in early 2019 a small Dutch lunar rover will travel to the moon.
The little 1.5 kg six legged robot will land on the lunar surface and will send images back home
to earth. For this mission the Dwingeloo radio telescope will become ‘mission control’!! The
launch will take place in India and on the same launch there will also be an Indian lunar rover. In
fact the plan is that the Indian and Dutch lunar rovers will take pictures of each other. It’s a
‘proof of concept’ mission. If this is successful a whole ‘swarm’ of little rovers will go to the
moon eventually. One planned mission is to build radio antennas to form an array for radio
astronomy



Now that GSLV-Mk-III is being used, will its higher payload capability permit this co-passenger ride to happen?

If this is going to happen, would everything be carried down on one lander?

Can anybody confirm?

Offline Phil Stooke

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #338 on: 08/29/2018 03:20 AM »
I think this is a payload with Team Indus.  The suggested date is presumably out of date, but they are still planning to fly to a landing site in Mare Imbrium.

Offline chota

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Re: Chandrayaan-2 GSLV MkIII NET January 2019
« Reply #339 on: 09/03/2018 11:29 AM »
Chandrayaan-2 base plate before the inclusion of the 5th Engine
« Last Edit: 09/03/2018 11:31 AM by chota »